Overpayment tax credits

Hi



i have received a letter from HMRC stating we owe 668.75 in overpaid tax credits(family tax credits actually) which confused me



i phoned them back about it and they told me it is connection with a failure to notify a child leaving education in 2005!!!!



Am I right to say this should be statute barred as I have no recollection of any correspondence relating to this?



if so how do I go about contesting it or is the fact that it is HMRC a no go



thanks in advance

Overpayment tax credits